A vehicle such as an electric vehicle (EV) or a plug-in hybrid vehicle includes rechargeable batteries such as lithium-ion batteries. A rechargeable battery is a power storage device that stores power supplied to an electric motor serving as a prime mover. The rechargeable battery includes an electrode assembly and a case that accommodates the electrode assembly. The electrode assembly includes a rectangular positive electrode including a positive electrode active material layer and a rectangular negative electrode layer including a negative electrode active material that are stacked with a separator arranged between the positive electrode and the negative electrode. Patent Documents 1 to 3 each disclose a structure in which the electrodes and the separator of the electrode assembly are fastened with fastening tapes.
To increase the contact properties of each electrode and limit displacement of each electrode, load may be applied in the stacking direction of the electrodes to regions opposing the active material layers. Further, when the electrode assembly expands during charging and discharging, the case may apply load to the opposing regions. In addition, in an assembled battery including a plurality of stacked power storage devices that are connected in series to one another, a constraining load may be applied in the stacking direction to each of the power storage devices. In these cases, ion deposits resulting from electrical conduction easily collect at a portion where the gap is large between the electrode assembly and the inner surface of the case.
Further, the load applied from the case is apt to concentrate at the fastening tape located between the electrode assembly and the inner surface of the case. Thus, the load applied to the fastening tape has a tendency to become uneven depending on the applied position of the fastening tape. This may generate ion deposits.
Referring to FIG. 5, Patent Document 1 describes a rechargeable battery in which fastening tapes 112 are applied to each of two side ends 111 of an electrode assembly 110. That is, the ends of the electrode assembly 110 other than the side ends 111, namely, an upper end 113 and a lower end 114 are not fastened by the fastening tapes 112. This may displace the upper end 113 and the lower end 114 of each electrode in the electrode assembly 110.
Referring to FIG. 6, Patent Document 2 describes a rechargeable battery in which fastening tapes 122 are applied to two side ends 121, an upper end 123, and a lower end 124 of an electrode assembly 120. The fastening tape 122 applied to the upper end 123 of the electrode assembly 120 is located between positive electrode tabs 125 and negative electrode tabs 126 that project from the upper end 123. Thus, the fastening tape 122 may hinder the impregnation of the electrode assembly 120 with electrolytic solution between the electrodes.
Referring to FIG. 7, Patent Document 3 describes a rechargeable battery in which fastening tapes 132 are applied to two side ends 131, an upper end 133, and a lower end 134 of an electrode assembly 130. In this case, the fastening tapes 132 are applied entirely to the side ends 131 of the electrode assembly 130. Thus, as compared to when the fastening tapes 132 are partially applied to the side ends 131, a wider range of the electrode assembly 130 receives load from the fastening tapes 132.